Invented in the French Alps in the 1960s, timeshare allows one to own a portion of a resort. The basic concept is like a condo, but for only a week every year.
For example:
Say you found a nice resort in Orlando. You could buy a week in a condo at that resort so you could see the rat every year. That week would either be fixed, e.g. week 23, or floating, e.g. summertime. Every year you could go back to that resort for your week.
If you didn't want to go to your resort, you could exchange your week with someone else at another resort. Exchange companies like RCI and II facilitate this trading.